Material end-plugging for the Scylla IV-P linear theta pinch

Scylla IV-P is a 5-m linear theta pinch at the Los Alamos Scientific Laboratory primarily used to study end effects of linear theta-pinch plasmas. One method that may be used to reduce plasma end loss from linear theta pinches is to insert material end plugs. Two different assemblies that insert end plugs have been fabricated and installed on Scylla IV-P. The presence of the material end plugs have been found to increase the plasma confinement time by 20 to 30 percent; the plasma stability is increased (the m = 1 wobble is suppressed), and the neutron production is not degraded. The design of the end plug insertion mechanisms is described in some detail and information is presented on end plug erosion. Material eroded from the end plug must be either removed by the vacuum system or it plates out on the vacuum system surfaces. A condensed gas end plug has been proposed to eliminate problems associated with ablated solid material; a third end plug assembly for this is being designed which inserts a cryostat coated with a condensed gas. A prototype of this cryogenically cooled end plug (cryo-plug) has been fabricated and tested. These data are presented and the insertion mechanism described